Function ncvisual_from_palidx 

pub unsafe extern "C" fn ncvisual_from_palidx(
    data: *const c_void,
    rows: c_int,
    rowstride: c_int,
    cols: c_int,
    palsize: c_int,
    pstride: c_int,
    palette: *const u32,
) -> *mut ncvisual

ncvisual_from_rgba(), but ‘data’ is ‘pstride’-byte palette-indexed pixels, arranged in ‘rows’ lines of ‘rowstride’ bytes each, composed of ‘cols’ pixels. ‘palette’ is an array of at least ‘palsize’ ncchannels. It is an error if ‘rows’, ‘cols’, ‘rowstride’, or ‘pstride’ are not positive, if ‘rowstride’ is not a multiple of ‘pstride’, or if ‘rowstride’ is less than ‘cols’ * ‘pstride’.